Isn't there only one cut available at Tiffany?
Yes, you want the best cut you can, Ideal or Excellent. Without the best cut, it won't sparkle. There's no need to really go that high in clarity, and will allow your budget to stretch more. You can pretty much figure that you are looking at roughly 25K usd outlay for a 1.5 ct stone. If you can go UNDER that mark like a 1.48 or something it will save you money, believe it or not. The even numbers carry a premium. 1ct stones at Tiffany tend to run right around 10k as a median number, obviously better cut, color and clarity will come with a higher premium than an H-I/VS2. I saw a 1.15 H VS2 about a year ago that was 15,000.
If you are willing to sidestep the brand, start your own thread on here with some specifications and your budget and we can help you find something through an online vendor who can ship to you where you are presently stationed.